The changes of the clinical picture of 12 epileptic patients with massive spasms when treated by Nitrazepam were studied. The treatment was satisfactory in 11 patients. In two cases the seizures were abolished since the first day; in 9 there was marked reduction of the intensity of spasms since the first day. With the treatment it was observed that (1) the spasms continued with its massive aspect, although the amplitude and violence of muscular contraction were reduced, (2) partial seizures occurred in some patients, and (3) the massive aspect of myoclonia disappeared, decreasing the repetitive tendency of the seizures. The interval of time between the onset of massive spasms and the beginning of the treatment by the Nitrazepam, as well as the insucess with previous anticonvulsive treatment, including ACTH, did not influence the results obtained with the Nitrazepam. It was observed that partial seizures relapsed, after a medium or a long period of time, in 7 patients and were related to decrease of the drug or to infectious processes. In 3 cases, the seizures control was more difficult after the relapse. Infectious processes of the respiratory tract were more frequently seen after the beginning of the treatment. During the treatment 7 patients developed generalized seizures, for the first time, and could be grouped in (1) early seizures, with onset between 2 weeks and one month of treatment and which disappeared spontaneously in 3 months, and (2) late seizures, with onset after 5 to 13 months of treatment. The early seizures, opposite to the late seizures, were not related to the reduction of the dosage or with intercurrent infectious processes. Some critical symptom and behavioral changes were observed when the late tonic seizures developed, suggesting the instalement of Lennox syndrome, although incomplete.